Biomarkers are characteristic biological features which can be measured objectively and can point to a normal biological or abnormal process in the body. A biomarker can be cells, genes, gene products or certain molecules such as enzymes or hormones. Complex organ functions or characteristic changes in biological structures are used as medical biomarkers. Reliable diagnosis of the disease is essential especially in the case of chronic diseases, for the treatment of which the patient potentially has to take medication, with the corresponding side effects, for a number of years. In this respect biomarkers are becoming ever more important because they can secure a difficult diagnosis or even enable it in the first place.
The treatment of psychiatric diseases such as depression, states of anxiety, manias, schizophrenia, etc., constitutes a considerable challenge. The positive effect of pharmacological active ingredients such as (selective) serotonin-re-uptake inhibitors (S)SRI), neuroleptica, etc. typically requires several weeks to improve the symptoms and months to years for healing. The dilemma arises therefrom for the patient and doctor of weighing up the sometimes severe side effects which worsen symptoms against the long-term effect of the medication. Until now the success of forms of treatment such as sport in cases of depression or anxiety states has been difficult to measure and integrate in a treatment.
Various magnetic resonance imaging methods have been evaluated in research which may be of significance to diagnostics and differential diagnostics as well as to treatment monitoring. Four magnetic resonance imaging methods are briefly presented here.
1. Resting state functional magnetic resonance imaging (resting-state fMRI or rsfMRI) determines by means of BOLD-EPI data the connectivity between individual areas of the brain which are functionally connected to each other. These different areas of the brain are called resting state networks and communicate with each other, such as, for example, the amygdala as the center of emotional processing, the thalamus as the hub for the distribution of sensory input, the hippocampus as short-term memory and learning or the prefrontal cortex for conscious planning and control. There are clear indications that the resting state fMRI method is suitable for the single diagnosis of patients, i.e. the rs-fMRI method has the stability and robustness required for a clinical application.
2. Arterial Spin Labeling (ASL) is a method of magnetic resonance imaging in which the perfusion in the human tissue is measured with an endogenous tracer—i.e. non-invasively. ASL is based on the fact that the proton spins in the blood of the arteries are magnetically marked upstream to the imaging layer. ASL is also used for example to measure a local increase in the blood perfusion in individual regions of the brain.
3. Morphometric methods in turn aim at measuring the size of different regions of the brain. Treatments such as the administering of SSRIs have the effect for example of increasing the size of the amygdala, and this, in turn, can be associated with emotional recovery.
4. Magnetic resonance spectroscopy is also used to determine conclusions about abnormal changes in individual areas of the brain.